Pole pieces



Nov. 17, 1959, w. L. CARLSON 2,913,603

POLE PIECES Filed Aug. 20, 1957 r 2 Sheets-Sheet 1 Fig. 3

I I INVENTOR. Wilbur L. Car/son dA fzw'lul His A Home Nov. 17, 1959 w.L. CARLSON 2,913,503

POLE pmczs Filed Aug. 20, 1957 v 2 Shuts-Sheet 2 Wilbur L. Car/son BY FI g. 4 MW H/s Attorney United States PatentO POLE PIECES Y Wilbur L.Carlson, Rochester, N.Y., assignor to General Motors Corporation,Detroit, Mich., a corporation of Delaware Application August 2.0, 1957,semi No. 679,206 Claims. c1. m n

This invention pertains to dynamo electric machines, and particularly topole pieces for electric motors.

Heretofore, it has been common practice to utilize suitably shapedstacked laminations in the manufacture of small direct current motors.In order to reduce the cost of manufacture of such small motors, it hasbeen proposed to substitute separate poles, or a single pole, and aframe for the stacked laminations, the pole pieces being composed ofeither sintered iron or steel. The present invention relates to a sheet.metal pole piece and method of making same which is much cheaper thanpole pieces composed of either sintered iron or solid steel.Accordingly, among my objects are the provision of a sheet metal polepiece having integral mounting means; the further provision of a methodof making sheet metal pole pieces having integral mounting means; thefurther provision of a sheet metal pole piece having separate mountingmeans; and the still further provision of a method of making a sheetmetal pole piece having separate mounting means. i

The aforementioned and other objects are accomplished in the presentinvention by forming a pole body and a pair of pole shoes from anintegral strip of sheet metal, such as steel. Specifically, twoembodiments of the present invention are disclosed herein. In thepreferred embodiment, the pole piece is composed of two pieces of sheetsteel, one of which is formed with a mounting tang and is also utilizedduring the forming operation. The other piece of sheet metal is bentaround three sides of the mounting tang element and forms the pole bodyand the pole shoes.

The steps involved in making the preferred pole piece comprise locatingthe tang element in a plane perpendicular to the sheet metal strip;placingthe elements in forming dies; applying pressure to the sheetmetal strip so as to bend the same in'a zig zag fashion about the tangelement; and thereafter placing the partially formed pole piece in acoining machine to deform the pole shoes into an arcuate configurationwhile simultaneously forming the pole body to the desired configuration.

In the second embodiment, the pole piece is composed of an integralstrip of sheet metal having pairs of notches in its marginal edgestogether with slits extending towards the center of the strip. Thenotched and slit portions form tangs for mounting the pole piece in amotor frame when the pole piece is formed to the final configuration.

The steps involved in making the pole pieces of the second embodimentcomprise notching and slitting the steel strip; placing the steel stripin the forming dies, and actuating the dies so as to bend the strip in azig zag fashion; and thereafter placing the pole piece in a coiningmachine to form the pole shoes into an arcuate configuration and todeform the pole body in the desired configuration.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawings, where- "ice in preferred embodiments of the present inventionare clearly shown.

In the drawings:

Figure l is a perspective view of a sheet metal strip for forming a-polepiece constructed according to one embodiment of this invention.

Figure 2 is an end view in elevation of a partially formed pole piececonstructed according to the first embodiment of this invention.

Figure 3' is an end view in elevation of the final configuration of apole piece constructed according to one embodiment of this invention.

Figure 4 is a fragmentary view in elevation of a motor incorporating apole piece constructed according to one embodiment of this invention.

Figure 5 is a sectional view taken along line 5--5 of Figure 4 withcertain parts removed.

Figure 6 is a perspective view of the metal pieces utilized to make apole piece according to the preferred embodiment of this invention-Figure 7 is a side view in elevation of the pieces shown in Figure 6.

Figure 8 is'a view in elevation depicting an intermediate step in theforming operation.

Figure 9 is an end view in elevation of the partially completed polepiece constructed according to the preferred embodiment.

Figure 10 is an end view in elevation of the final configuration of thepole piece constructed according to the preferred embodiment.

Figure 11 is a side view in elevation taken in the direction of arrow 11of Figure 10.

With particular reference to Figures 1 through 3, in one embodiment ofthe present invention, the pole piece comprises a single strip 20 ofsheet metal, such as steel. The strip 20 has a greater width thanthickness as shown in Figure 1, and the opposed marginal edges thereofare formed with notches 21 which connect with slots 22 extendinginwardly therefrom. The strip of metal 20 is bent in zig zag fashionabout phantom lines 23 as indicated in Figure l by forming dies, notshown, to the configuration shown in Figure 2. The metal piece shown inFigure l is not the final configuration of the pole piece, but ratherthe configuration after the strip of sheet metal leaves the forming dieswhich bend the metal back and forth upon itself so that the intermediateportion thereof forms a pole body designated by the numeral 24 with fourtangs 25 extending therefrom. The tangs 25 are formed by reason of themarginal edges of the strip 20 being notched and slotted asaforedescribed prior to insertion in the forming dies. In addition, theends 26 and 27 of the strip are disposed at right angles to the bodyportion 24 in the intermediate configuration.

Thereafter, the article as shown in Figure 2, is placed in a coiningmachine, and during the coining operation the pole body 24 assumes thefinal configuration as shown in Figure 3, and the ends 26 and 27 aredeformed to an arcuate configuration constituting pole shoes. The tangs25 extend upwardly from the pole portion 24 and are utilized forattaching the pole piece to a motor frame.

Referring to Figures 4 and 5, an electric motor of the general typedisclosed in copending application Serial No. 664,009, filed June 6,1957, in the name of Simmons et al., and assigned to the assignee ofthis invention, is disclosed. This motor comprises a unitary sheet metalframe 30 having overlapping end portions 31 and 32, the side 33 of theframe opposite the overlapping ends being of arcuate configuration andconstituting one pole of the motor. The overlapping end portions 31 and32 of the frame have aligned apertures 34 and 35 respectively, throughwhich the tangs 25 of the pole piece extend. In addition, a pole plate36 of magnetic material is welded to the outer periphery of the arcuateportion 33 to improve the flux distribution. The tangs 25 of the polepiece extend through the aligned apertures 34 and 35 of the overlappingend portions 31 and 32, re-. spect'ively, and are thereafter swedged, orotherwise deformed, so as to rigidly interconnect the ends of the framewhile simultaneously securing the pole piece in position. The pole bodyis encircled by a field coil 3-7, and an armature of conventionalconstruction is rotatably journalled in the end plates of the motorframe between the pole shoes .26 and 27 and the arcuate pole portion 33of the frame.

With particular reference to Figures 6 through 11, the preferredembodiment of a pole piece constructed according to this invention will.be described. In the preferred embodiment, the pole piece is composedof two pieces of metal, namely a steel strip 49 having a greater Widththan thickness, and a steel piece 50 having a tang portion 51. The steelstrip 40 and the steel piece 50 are placed in the forming dies at rightangles to each other as viewed in Figures 6 and 7, and during the firstoperation of the forming dies, the strip 40 is bent as indicated inFigure 8 so that the ends 41 and 42 thereof remain in a plane at rightangles to that of the piece 50 while the intermediate portion is of zigzag shape. Thereafter, the strip 40 is bent around three sides of thepiece 50 by having its intermediate portion bent upon itself and on bothsides of the piece 50. As a final operation, the article shown in Figure9 is placed in a coining machine so as to deform the final configurationof the pole body designated by the numeral 43. In addition, during thecoining operation the tang 51 is formed with tapered ends as indicatedby numeral 52. The completed pole piece constructed according to thepreferred embodiment is shown in Figures 10 and 11, it being understoodthat the pole piece shown in Figures 10 and 11 can be used in the motoras shown in-Figures 4 and if the overlapping end portions 31 and 32 haveonly a single pair of aligned apertures therein.

From the foregoing it is readily apparent that the pole piecesconstructed according to the present invention can be readily producedat substantial savings over solid steel pole pieces of the type shown inthe aforementioned copending application. Moreover, by making polepieces according to the preferred embodiment of this invention, theseparate mounting piece in effect constitutes part of the forming diesduring the intermediate forming operation and eliminates the expensivenotching and slitting operations of the pole piece constructed accordingto the modified embodiment of this invention.

While the embodiments of the invention as herein disclosed constitutepreferred forms, it is to be understood that other forms might beadopted.

What is claimed is as follows:

1. A pole piece comprising, a single strip of sheet metal having itsintermediate portion bent to form a pole having its intermediate portionfolded back and forth upon itself to form a pole body having a thicknessequal to at least four times the thickness of said strip, opposite endsof said strip being formed to constitute pole shoes.

5. The pole piece set forth in claim 4 wherein said intermediate portionof said strip is folded about a second metal piece constituting mountingmeans.

6. The pole piece set forth in claim 4 wherein said strip has marginalnotches and inwardly extending slots connecting with said notches so asto form integral mounting tangs, and wherein said pole body has athickness equal to six times the thickness of said strip.

7. A pole piece comprising, a strip of sheet metal having itsintermediate portion formed to constitute at least the major portion ofa pole body and the ends formed to constitute pole shoes; and mountingmeans extending from said pole body comprising a separate piece of metalabout which the intermediate portion of said strip is folded.

8. A pole piece comprising, a strip of sheet metal having itsintermediate portion folded upon itself to form a pole body having athickness equal to at least twice the thickness of said strip, oppositeends of said strip being formed to constitute pole shoes.

9. A pole piece comprising, a single strip of sheet metal having itsintermediate portion folded back and forth upon itself to form a polebody having a thickness equal to at least four times the thickness ofsaid strip, opposite ends of said strip being formed to constitutearcuate pole shoes.

10. A pole piece comprising, a single strip of sheet metal having itsintermediate portion bent to form a pole body and its ends formed toconstitute arcuate pole shoes which extend in opposite directions fromthe pole body.

References Cited in the file of this patent UNITED STATES PATENTS2,764,802 Feiertag Oct. 2, 1956 FOREIGN PATENTS 63,061 Denmark Dec. 18,1944

